The present invention relates to the fixation of water-soluble, carboxyl-containing vinyl monomers on fibrous substrates in the form of polymeric compositions and to the method of accomplishing the same.
Methods have been provided for the deposition of preformed polymeric materials on fibers or fabric substrates and for the development of graft polymers on fibrous or fabric substrates. The deposition of preformed polymers provides a means for modifying the surface properties of fibers and fabrics, but this method is characterized by several limitations and deficiencies. The preformed polymer is viscous if dissolved in the medium in which it is applied; or it is present in a particulate form as an emulsion or dispersion in a continuous phase which is often water. In either case the penetration of the polymer into the fabric or the yarns or the fibers occurs slowly, being limited by the size of the dispersed particles or the size of the molecular species. As a consequence, penetration is limited and is relatively poor, polymer concentrates at fiber crossover points, and stiffness becomes pronounced even at low levels of polymer deposition.
In the case of graft polymerization on fibers and fabric substrates, numerous methods are now known for accomplishing such reactions. The most common reactions involve free-radical initiation by one of a variety of means such as peroxide catalyst, high or low energy irradiations, heat, oxidation-reduction reactions, and electrical discharge. Each of these means of generating free radicals is subject to practical limitations as described by K. Hoshino in Chemical Aftertreatment of Textiles, ed. H. F. Mark, M. S. Wooding, and S. M. Atlas, Chapter VB, p. 235, Wiley-Interscience, New York, 1971, by E. H. Immergut in Encyclopedia of Polymer Science and Technology, Vol. 3, p. 242, Interscience Publishers, New York, 1965, and by J. C. Arthur, Jr. in Macromolecular Chemistry, Vol. 2, p. 1, Academic Press, London, 1970.
Two interrelated problems appear to be responsible for the difficulties experienced in thorough cleaning (and preventing soil staining) of fabrics composed of polyester, nylon, or durable-press synthetic fiber/cotton blends in aqueous wash baths such as employed in home and commercial laundry washing machines. Compared to unmodified cotton, synthetic fibers and durable-press cotton fibers display somewhat more hydrophobic surface properties that prevent good water penetration in the fibers for removal of soil therefrom; moreover, synthetic fibers are of an oleophilic nature. Thus the first problem involves the attraction of dirt and oily grime to the synthetic fibers; these become embedded therein and are not removed during subsequent washing cycles because of the inability of water to thoroughly penetrate the synthetic fibers in a manner similar to the swelling of unmodified cellulosic fibers in water. Second, and also due to the above described surface properties, oily soil materials that are washed out of the fabric during the laundering operation are continuously attracted to the surface of the fabric and become redeposited thereon. As a result, the fabric never returns to a truly clean condition and, instead, assumes a discolored, stained appearance which eventually renders it unfit for further use. The present invention obviates the problem of soiling and staining by modifying the surface characteristics of natural and synthetic fiber-containing fabrics, as fully disclosed hereinafter.
A substantial increase in the hydrophilic characteristics of chemically modified or finished cotton, cotton/synthetic fiber blends, and synthetic fibers is desirable and consistent with improvements in antistatic characteristics and comfort in apparel as well as improvements in soil release and the reduction in soil redeposition.
It is accordingly a primary object of the present invention to provide for a deposition and polymerization of water-soluble carboxyl-containing vinyl monomers, alone and in combination with other vinyl monomers, in and on fibrous and fabric substrates in a single stage operation utilizing a single aqueous reaction medium for conveying the reactions systems to the fibers or fabrics.
It is further object of the present invention to provide a simplified method of simultaneous polymerization and crosslinking to form a network polymeric material deposited in and on the fibrous or fabric substrate in a highly durable manner.
It is another object of the present invention to provide a process of fixing polymers on fibrous and fabric substrates with high efficiency of conversion of monomers so that the monomers are neither wasted by polymerization in a solution phase away from the substrate nor are lost by volatilization in the curing step.
It is a still further object of the present invention to produce chemically modified fibers and fabrics that are improved in hydrophilic characteristics, comfort, soil release, resistance to soil redeposition, antistatic properties, dyeing behavior, and pleasing hand.
It is an additional object of the present invention to achieve the modification of surface and bulk properties of fibers, yarns, and fabrics by an efficient polymerization and fixation of monomers, which reactions do not depend upon grafting or polymer chain initiation from the molecular chains of the substrates for development of durable fixation of the polymer to the substrate.
It is another object of this invention to provide a process for the fixation of polymers in and on fibrous substrates, which process is free of one or more of the limitations or disadvantages of prior art coating processes involving preformed polymers or prior art graft polymerization processes.